1. Field of the Invention
The present invention relates to an endoscope apparatus having an image pickup device in a distal end portion of an insertion portion.
2. Description of the Related Art
Conventionally, endoscope apparatuses have been widely used in an industrial field and a medical field. An image pickup device is disposed at a distal end of an insertion portion, and an endoscopie image obtained by an image being picked up by the image pickup device is displayed on a display apparatus of a main body portion that is connected to the insertion portion.
Endoscope apparatuses have elongated insertion portions, and are used under various temperature environments such as inspection of the insides of jet engines under high-temperature environments, and inspection of water pipes in cold districts.
It becomes difficult for image pickup devices such as a charge coupled device (hereinafter, called CCD) of recent years to sample image signals that are video signals stably due to high frequency drive accompanying increase in density of pixels, and variations in signal waveforms of output signals (for example, called CCDout) that are outputted from the image pickup devices accompanying temperatures. For the purpose of temperature compensation, for example, Japanese Patent Application Laid-Open Publication No. 8-18871 proposes the art of correcting the intensity change of the video signal which is outputted by the CCD by gain adjustment based on the temperature.
Since endoscope apparatuses are used under various temperature environments, stable image qualities are required as inspection apparatuses in the use environments at various temperatures.